Thermodenuder and method for removing semi-volatile material and semi-volatile particles from an aerosol

ABSTRACT

A thermodenuder having a main tube with an outer wall, and a heater ( 23 ) arranged within the main tube. The heater is arranged in the center of a cross section through the main tube and is spaced apart from the outer wall of the main tube. The main tube has a main axis of extension, and the heater extends parallel to the main axis. The main tube has two openings that are arranged at opposing side faces of the main tube. A channel for an aerosol is arranged within the main tube between the heater and the outer wall and between the two openings. Furthermore, a method for removing semi-volatile material and semi-volatile particles from an aerosol is provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application Ser.No. 63/012,631, filed Apr. 20, 2020, which is incorporated herein byreference in its entirety.

The present invention relates to a thermodenuder and a method forremoving semi-volatile material and semi-volatile particles from anaerosol.

Thermodenuders are employed to remove semi-volatile material andsemi-volatile particles from the nonvolatile particles of an aerosol.Typically, the semi-volatile material and semi-volatile particles areevaporated so that the nonvolatile particles remain. For this purposethe aerosol is heated so that the semi-volatile material andsemi-volatile particles are evaporated. Subsequently, the aerosol andthe evaporated semi-volatile material are cooled down so that thesemi-volatile material is adsorbed by an adsorbent material or surface.

However, two processes can reduce the efficiency of removingsemi-volatile material and semi-volatile particles from nonvolatileparticles of an aerosol. At first, the evaporated semi-volatile materialcan nucleate and form additional particles instead of being adsorbed. Atsecond, the evaporated semi-volatile material can re-adsorb on thenonvolatile particles of the aerosol again.

It is an objective to provide a thermodenuder that can be operatedefficiently. It is further an objective to provide an efficient methodfor removing semi-volatile material and semi-volatile particles from anaerosol.

These objectives are achieved with the independent claims. Furtherembodiments are the subject of dependent claims.

In at least one embodiment of the thermodenuder, the thermodenudercomprises a main tube with an outer wall. The outer wall forms the maintube. The main tube can have the shape of a cylinder which is formed bythe outer wall. The main tube can be closed at both sides of thecylinder except for two openings. The outer wall surrounds an innervolume of the main tube. The main tube can also have any other shape,for example a rectangular shape. The main tube can comprise stainlesssteel.

Another expression for the thermodenuder is a thermodesorber.

The thermodenuder further comprises a heater arranged within the maintube. The heater can be arranged completely within the main tube. Theheater can be a resistive heater. This means, the heater can comprise anelectrically conductive material. For example, the heater comprises anelectrically conductive wire. The heater is configured to be heated to atemperature of at least 20° C. and at most 400° C. This means, thethermodenuder is configured to heat an aerosol within the thermodenuderto a temperature of at least 20° C. and at most 400° C. Thethermodenuder can furthermore be configured to control the temperatureof the heater.

The main tube has a main axis of extension. The main axis of extensionrefers to the axis along which the cylinder extends. Within a cylinderthe main axis of extension relates to the vertical direction. The mainaxis of extension of the main tube connects two side faces of the maintube that extend parallel to each other.

The heater is arranged in the center of a cross section through the maintube. The cross section through the main tube can be given in a planethat is perpendicular to the main axis of extension of the main tube. Inthis cross section the main tube has a circular shape. The heater isarranged in the center of the circle in this cross section. This means,in this cross section the heater is surrounded by the outer wall of themain tube in all directions. It is further possible that the crosssection through the main tube is given in a plane to which the main axisof extension of the main tube runs parallel. This cross section can be acut through the center of the main tube. In this cross section theheater is arranged in the center of the main tube and extends along themain axis of extension of the main tube. In this cross section the outerwall of the main tube is arranged above and below the heater. That theheater is arranged in the center of a cross section thorough the maintube can mean that the heater is arranged approximately in the center ofa cross section through the main tube. It can further mean that at leasta part of the heater is arranged in the center of a cross sectionthrough the main tube.

The heater is spaced apart from the outer wall of the main tube. Thismeans, the heater is not in direct contact with the outer wall of themain tube. The heater is arranged at a distance to the outer wall of themain tube. In a cross section through the main tube in a plane thatextends perpendicular to the main axis of extension of the main tube thedistance between the heater and the outer wall is the same in eachdirection.

The heater extends parallel to the main axis of extension of the maintube. This means at least a part of the heater extends parallel to themain axis of extension of the main tube. The heater can have anelongated shape. Furthermore, the heater can have a straight shape.

The main tube has two openings which are arranged at opposing side facesof the main tube. The opposing side faces can be the side faces of acylinder that extend parallel to each other. The openings can each besmaller than the area of the side faces. The openings can have acircular shape. The diameters of the openings can be larger than thediameter of the heater. The diameters of the openings are large enoughso that an aerosol can pass each of the openings. In cross sectionsthrough the main tube in planes that extend perpendicular to the mainaxis of extension of the main tube the openings are each arranged in thecenter of the main tube. This means, the openings are each arranged inthe center of the respective side face. The two openings and the heaterlie on a straight line that extends parallel to the main axis ofextension of the main tube.

A channel for an aerosol is arranged within the main tube between theheater and the outer wall and between the two openings. This means thechannel is formed between the heater and the outer wall and between thetwo openings. The size of the channel is large enough so that an aerosolcan pass through the channel. The channel connects the two openings witheach other. Furthermore, the channel extends along the heater. Thechannel extends along the main axis of extension of the main tube. In across section through the main tube in a plane that extendsperpendicular to the main axis of extension of the main tube the channelsurrounds the heater. The channel can surround the heater in alldirections in the cross section. The aerosol can be for example exhaustfrom an engine.

The thermodenuder described herein can be employed to removesemi-volatile material and semi-volatile particles from nonvolatileparticles of an aerosol. This means, semi-volatile material andsemi-volatile particles can be separated from nonvolatile particles ofan aerosol. For this purpose an aerosol is provided to one of theopenings of the main tube and led into the main tube. Within the maintube the aerosol moves within the channel along the main axis ofextension of the main tube. This means, the aerosol enters the main tubethrough one of the openings and leaves the main tube through the otheropening. When moving through the channel the aerosol is heated by theheater. In this way semi-volatile material and semi-volatile particlesof the aerosol are evaporated. The outer wall of the main tube is incontact with the surroundings of the main tube. The surroundings of themain tube are cooler than the heater. Therefore, a temperature gradientis present within the main tube during operation of the thermodenuder.The temperature gradient runs from the center of the main tube where theheater is arranged to the outer wall. This means, within the main tubethe temperature in the vicinity of the heater is higher than thetemperature in the vicinity of the outer wall. The material and theparticles evaporated from the aerosol can adsorb on the outer wall or onan adsorbent material arranged within the main tube. The aerosol withthe remaining nonvolatile particles is led out of the main tube.

The evaporated semi-volatile material and semi-volatile particles canmove within the main tube and adsorb on colder surfaces as the outerwall or an adsorbent material. On these surfaces the evaporatedsemi-volatile material and semi-volatile particles are cooled because ofthe cooler environment. Thus, the semi-volatile material andsemi-volatile particles stay at the surface where they are adsorbed.

In this way an adsorption of semi-volatile material on other evaporatedmaterial or on nonvolatile particles of the aerosol is reduced. Theevaporated semi-volatile material is first adsorbed, for example on theouter wall, and then cooled down. This means, when the semi-volatilematerial is cooled it is already separated and spaced apart from theremaining nonvolatile particles of the aerosol. This reduces theprobability for a re-adsorption of semi-volatile material on nonvolatileparticles of the aerosol. Because of the temperature gradient within themain tube the adsorption capacity is maximized at positions within themain tube that are closer to the outer wall than to the heater. At thecolder positions closer to the outer wall the adsorption capacity isincreased in comparison to positions close to the heater. This means, aregion for the adsorption of evaporated semi-volatile material is formedspaced apart from the heater and the remaining nonvolatile particles.Thus, a re-adsorption on nonvolatile particles is avoided.

Another advantage of the thermodenuder is that the temperature of theaerosol can be changed quickly. The aerosol within the channel is indirect contact with or close to the heater. In order to heat the aerosolit is not necessary to heat any other material because the aerosol isdirectly heated by the heater. This setup enables a faster temperaturechange than a setup where the heater is arranged around the main tube.

In addition, the setup of the thermodenuder is compact since only onemain tube is required.

In at least one embodiment of the thermodenuder, an adsorbent materialis arranged within the main tube between the outer wall and the heater.It is possible that the adsorbent material is in direct contact with theouter wall. Alternatively, the adsorbent material is arranged spacedapart from the outer wall. In a cross section through the main tubewithin a plane that extends perpendicular to the main axis of extensionof the main tube the adsorbent material surrounds the heater in alldirections. Along the main axis of extension of the main tube theadsorbent material can have the same extent as the main tube. Thismeans, the adsorbent material extends over the whole length of the maintube. The adsorbent material can be a porous material. This means, theadsorbent material has a large surface where semi-volatile material canadsorb. For example the adsorbent material comprises activated carbon,ceramic fiber, glass fiber or silica gel. During operation of thethermodenuder evaporated semi-volatile material of the aerosol canadsorb on or within the adsorbent material. For this purpose theadsorbent material has a large surface. In this way a large amount ofevaporated semi-volatile material can be adsorbed on or within theadsorbent material. Furthermore, during operation of the thermodenuderthe adsorbent material has a cooler temperature than the heater. Thus,the probability for evaporated semi-volatile material that is adsorbedon or within the adsorbent material to stay on or within the adsorbentmaterial is increased because the adsorbed semi-volatile material iscooled by the adsorbent material. Because of the temperature gradientand the cooler temperature of the adsorbent material the adsorptioncapacity of the adsorbent material is increased. In this way, theefficiency of removing volatile particles from nonvolatile particles ofthe aerosol is increased.

In at least one embodiment of the thermodenuder, the adsorbent materialis arranged spaced apart from heater. This means, the adsorbent materialis not in direct contact with the heater. In this way the temperaturegradient between the heater and the adsorbent material is achieved. Asthere is a distance between the adsorbent material and the heater theadsorbent material has a reduced temperature in comparison to the heaterduring operation of the thermodenuder. Thus, the aerosol within thechannel is heated by the heater during operation of the thermodenuder.The evaporated semi-volatile material that is adsorbed on or within theadsorbent material is cooled by the cooler adsorbent material and thusstays on or within the adsorbent material. In this way, the efficiencyof removing semi-volatile material and semi-volatile particles fromnonvolatile particles of the aerosol is increased.

In at least one embodiment of the thermodenuder, the adsorbent materialcomprises ceramic fiber. Ceramic fiber has a large surface. Therefore, alarge amount of evaporated semi-volatile material can be adsorbed on andwithin the ceramic fiber.

In at least one embodiment of the thermodenuder, an inner tube isarranged within the main tube between the adsorbent material and theheater, where the inner tube is permeable for gases and the channel isarranged within the inner tube. The inner tube can further be permeablefor semi-volatile material. The inner tube separates the adsorbentmaterial from the channel for the aerosol. Thus, the inner tube is indirect contact with the adsorbent material. The channel is formed withinthe inner tube. The inner tube has a cylindrical shape. The inner tubeis arranged completely within the main tube. The inner tube has the sameextent along the main axis of extension of the main tube than the maintube. In a cross section through the main tube in a plane that isperpendicular to the main axis of extension of the main tube the innertube surrounds the channel and the heater in all directions. The innertube is permeable for gases and particles. This means, the inner tube isporous. For example, the inner tube is formed by or comprises a wiremesh or a metal mesh. For example, the inner tube comprises Teflon. Inthis way, the evaporated semi-volatile material and semi-volatileparticles can move from the channel to the adsorbent material. The innertube is employed to prevent the adsorbent material from entering thechannel.

In at least one embodiment of the thermodenuder, a further channel isarranged between the outer wall and the adsorbent material. The furtherchannel is in direct contact with the outer wall and the adsorbentmaterial. The further channel has the same extent along the main axis ofextension of the main tube as the main tube. This means, the furtherchannel has the same length as the main tube. In a cross section throughthe main tube in a plane that is perpendicular to the main axis ofextension of the main tube the further channel surrounds the adsorbentmaterial in all directions. At one of the side faces of the main tube afurther opening is arranged that is connected with the further channel.The further opening is arranged closer to the outer wall than theopening. The further channel can be employed to remove adsorbedsemi-volatile material from the adsorbent material. This process canalso be called regeneration. After operating the thermodenuder for awhile a large amount of evaporated semi-volatile material is adsorbed onor within the adsorbent material. In order to enable the adsorption ofmore evaporated semi-volatile material and semi-volatile particles it isnecessary to remove the adsorbed semi-volatile material. This can beachieved by establishing a flow of gas or air through the furtheropening towards the opening on the opposite side of the main tube. Inthis way the flow of gas or air flows through the adsorbent material.With the flow of gas or air the adsorbed semi-volatile material can beremoved from the adsorbent material. The temperature of the air or gasis higher than the temperature of the adsorbent material. This means,the adsorbed semi-volatile material and semi-volatile particles areevaporated from the adsorbent material again and are carried out of themain tube by the flow of gas or air. In this way, the adsorbent materialis regenerated or cleaned. The regeneration or cleaning of the adsorbentmaterial is necessary for an efficient operation of the thermodenuder.

In at least one embodiment of the thermodenuder, one of the openings isconnected with a fitting. The fitting can be a valve. The main tube hastwo side faces, namely a first side face and a second side face. Theopening that is arranged at the first side face is referred to as thefirst opening. The first opening is connected with the fitting. Thefitting can be configured to control the flow of an aerosol towards themain tube. The fitting can be connected with another tube for leadingthe aerosol towards the main tube. The fitting can be connected to thechannel so that an aerosol can enter the main tube through the fittinginto the channel. Furthermore, the heater can be connected to thefitting. In this way, the heater can be fixed within the main tube. Theconnection of the heater to the fitting can be the only connection pointof the heater with a part of the main tube. The fitting enablesadvantageously to control of the flow of an aerosol within the maintube.

In at least one embodiment of the thermodenuder, the main tube has theshape of a cylinder. The cylinder is formed by the outer wall. In thisway the main tube has a symmetric shape and a uniform flow of an aerosolwithin the main tube is enabled.

In at least one embodiment of the thermodenuder, the heater extendsalong at least 80% of the length of the main tube parallel to the mainaxis of extension of the main tube. This means the heater can havenearly the same length as the main tube along the main axis of extensionof the main tube. In this way a uniform heating of the aerosol withinthe main tube is achieved. The geometry of the thermodenuder is chosenin such a way that there is a temperature gradient from the center ofthe main tube where the heater is arranged towards the adsorbentmaterial and the outer wall. Thus, a cooling of semi-volatile materialonly takes place at a distance to the heater where the adsorbentmaterial or the outer wall is arranged so that evaporated semi-volatilematerial can adsorb on the outer wall or on or within the adsorbentmaterial instead of on other particles. This is achieved by theextension of the heater along most of the length of the main tube. Acooling of the aerosol in the center of the main tube, where anadsorption of evaporated semi-volatile material is not desired, isavoided.

In at least one embodiment of the thermodenuder, the channel is indirect contact with the heater. The channel is the region where theaerosol is led through the main tube. Thus, the aerosol is led throughthe main tube directly around the heater. During operation, the aerosolwithin the main tube is in direct contact with the heater. Thisarrangement enables an efficient heating of the aerosol in the center ofthe main tube. The aerosol is not heated via another material butdirectly by the heater. In addition, this advantageously enables a fastchange of the temperature of the aerosol.

In at least one embodiment of the thermodenuder, one of the side facesof the main tube in which one of the openings is arranged is formed by acap that is reversibly attached to the main tube. The second side faceof the main tube is formed by a cap that is reversibly attached to themain tube. This means, the side face which is formed by a cap isarranged at the side of the main tube opposite to the side face wherethe fitting is arranged. The cap can have the shape of a circle. The capcan cover the whole second side face of the main tube. That the cap isreversibly attached to the main tube means that the cap can be removedand placed again at the main tube. When the cap is arranged at the maintube it closes the main tube. Employing the cap enables the replacementof the adsorbent material. For this purpose the cap is removed and theadsorbent material is taken out of the main tube. Afterwards, a newadsorbent material is placed in the main tube and the cap is placedagain at the main tube. It can be necessary to replace the adsorbentmaterial once a large amount of semi-volatile material is adsorbed on orwithin the adsorbent material.

Furthermore, a method for removing semi-volatile material andsemi-volatile particles from an aerosol is provided. The thermodenudercan preferably be employed in the methods described herein. This meansall features disclosed for the thermodenuder are also disclosed for themethod for removing semi-volatile material and semi-volatile particlesfrom an aerosol.

According to at least one embodiment of the method for removingsemi-volatile material and semi-volatile particles from an aerosol, themethod comprises the step of providing a main tube with an outer wall,where a heater is arranged within the main tube.

The method further comprises heating a volume surrounding the heater bythe heater. This means, the heater is employed to heat the surroundingsof the heater. If the heater is a resistive theater this can mean that avoltage is applied to the heater or an electrical current is led throughthe heater.

The method further comprises leading an aerosol through the main tubeand through two openings of the main tube where the two openings arearranged at opposing side faces of the main tube. A flow of the aerosolthrough the main tube can for example be established by employing a flowcontroller. The flow controller can be connected with one of theopenings of the main tube. The flow controller can be configured tocontrol the amount and the velocity of the aerosol led into the maintube. The aerosol enters the main tube through the first opening,traverses the main tube and leaves the main tube through the secondopening.

The heater is arranged in the center of a cross section through the maintube. The heater is spaced apart from the outer wall of the main tube.The main tube has a main axis of extension. The heater extends parallelto the main axis of extension of the main tube.

A channel for the aerosol is arranged within the main tube between theheater and the outer wall and between the two openings. This means, anaerosol being led through the main tube enters the main tube through thefirst opening, traverses the main tube through the channel and leavesthe main tube through the second opening.

According to at least one embodiment of the method, semi-volatilematerial and semi-volatile particles of the aerosol are evaporatedwithin the main tube. When passing through the channel the aerosol isheated by the heater. In this way semi-volatile material of the aerosolis evaporated. This means, semi-volatile material and nonvolatileparticles of the aerosol are separated from each other. The evaporatedsemi-volatile material and semi-volatile particles can adsorb on theouter wall or the adsorbent material. The remaining nonvolatileparticles leave the main tube through the second opening. This enables afurther analysis of the nonvolatile particles without the semi-volatilematerial.

According to at least one embodiment of the method, the main tube isheated from outside of the main tube. This means, outside of the maintube a further heater can be placed in order to heat the main tube. Forexample, the further heater is arranged adjacent to the outer wall. Inthis way, the outer wall and the adsorbent material are heated. Thus,semi-volatile material adsorbed on the outer wall or on or within theadsorbent material are evaporated. In this way, the outer wall or theadsorbent material are cleaned. This cleaning is necessary in order toenable an efficient operation of the thermodenuder.

According to at least one embodiment of the method, a gas flow isprovided through a further channel that is arranged between the outerwall and an adsorbent material that is arranged between the furtherchannel and the channel. The gas is led into the further channel througha further opening that is connected with the further channel. Thefurther opening is arranged within the first side face. The flow of thegas can be controlled by a flow controller. Furthermore, the gas ledinto the further channel is heated. This means, the temperature of thegas led into the further channel is higher than the temperature of theadsorbent material during operation of the thermodenuder. The gas ledinto the further channel traverses the adsorbent material and leaves themain tube through the second opening. As the gas is heated it also heatsthe adsorbent material. Therefore, semi-volatile material adsorbed tothe adsorbent material are evaporated again and transported out of themain tube with the flow of gas. In this way, the adsorbent material isregenerated or cleaned.

The following description of figures may further illustrate and explainexemplary embodiments. Components that are functionally identical orhave an identical effect are denoted by identical references. Identicalor effectively identical components might be described only with respectto the figures where they occur first. Their description is notnecessarily repeated in successive figures.

In FIG. 1 a cross section through an exemplary embodiment of thethermodenuder is shown.

In FIGS. 2 and 3 cross sections through further exemplary embodiments ofthe thermodenuder are shown.

FIG. 1 shows a cross section through the thermodenuder 20 according toan exemplary embodiment. The thermodenuder 20 has a cylindrical shape.The cross section is a cut through the center of the thermodenuder 20along the main axis of extension x of the cylinder. The main axis ofextension x of the thermodenuder 20 is the vertical axis of thecylinder. This means, the side faces 34, 35 at the left and right of thethermodenuder 20 are the circular shaped areas of the cylinder thatextend parallel to each other. The extent of the thermodenuder 20 alongits main axis of extension x can be less than 1 meter.

The thermodenuder 20 comprises a main tube 21 with an outer wall 22. Theouter wall 22 establishes the cylinder shape of the thermodenuder 20.Thus, the main tube 21 has the shape of a cylinder. The outer wall 22delimits the main tube 21. The outer wall 22 can comprise stainlesssteel or any other metal. The thermodenuder 20 further comprises aheater 23 which is arranged within the main tube 21. The heater 23 isarranged in the center of the main tube 21. In the cross section shownin FIG. 1 the heater 23 is arranged in the center surrounded by theouter wall 22. In a cross section in a plane which is perpendicular tothe plane shown in FIG. 1 the heater 23 is arranged in the center of themain tube 21 and is completely surrounded by the outer wall 22. Theheater 23 is not in direct contact with the outer wall 22 but spacedapart from the outer wall 22. The main tube 21 has a main axis ofextension x which runs parallel to the main axis of extension x of thecylinder. The heater 23 extends parallel to the main axis of extension xof the main tube 21. The heater 23 can be a resistive heater 23 in formof an electrical conductor extending along most of the extent of themain tube 21. The heater 23 extends parallel to the main axis ofextension x of the main tube 21.

The main tube 21 has two openings 24, 25 which are arranged at opposingside faces 34, 35 of the main tube 21. The two openings 24, 25 arereferred to as a first opening 24 and a second opening 25. The firstopening 24 is arranged within the first side face 34 one of the sidefaces 34, 35 of the main tube 21. The second opening 25 is arrangedwithin the second side face 35 of the side faces 34, 35 of the main tube21. The first opening 24 is connected with a fitting 30. The fitting 30completely fills the first opening 24. Through the fitting 30 an aerosolor a gas can be led into the main tube 21 which is shown by an arrow.The heater 23 is fixed to the fitting 30. The heater 23 is arranged atthe center of the fitting 30. Around the heater 23 is a passage 33 for agas or an aerosol within the fitting 30 so that an aerosol or a gas canbe led through the fitting 30 into the main tube 21. The fitting 30 hasan inlet 32 where an aerosol or a gas can be provided to the fitting 30.

Within the main tube 21 a channel 26 for an aerosol is arranged betweenthe heater 23 and the outer wall 22 and between the two openings 24, 25.The channel 26 extends from the passage 33 within the fitting 30 to thesecond opening 25. This means, the channel 26 extends between the twoopenings 24, 25. Furthermore, the channel 26 is adjacent to the heater23. This means, the channel 26 is in direct contact with the heater 23.

Within the main tube 21 an adsorbent material 27 is arranged between theouter wall 22 and the heater 23. The adsorbent material 27 can compriseactivated carbon. Furthermore, the adsorbent material 27 is arrangedspaced apart from the heater 23 so that it is not in direct contact withthe heater 23.

The channel 26 is formed within an inner tube 28 that is arranged withinthe main tube 21 between the adsorbent material 27 and the heater 23.The inner tube 28 is permeable for gases and semi-volatile material. Theinner tube 28 separates the adsorbent material 27 from the channel 26.The adsorbent material 27 fills the whole space between the inner tube28 and the outer wall 22. The channel 26 fills the whole space withinthe inner tube 28 which is not occupied by the heater 23. Thus, thechannel 26 is a cavity within the main tube 21 where an aerosol can passthrough the main tube 21.

With FIG. 1 the method for removing semi-volatile material andsemi-volatile particles from an aerosol is described. According to themethod the main tube 21 with the outer wall 22 is provided, where theheater 23 is arranged within the main tube 21. A volume surrounding theheater 23 is heated by the heater 23. In this way a temperature gradientis established which is shown by an arrow extending from the center ofthe main tube 21 to the outer wall 22. This means, the temperature inthe vicinity of the heater 23 is higher than the temperature in thevicinity of the outer wall 22. Furthermore, an aerosol is led throughthe main tube 21 and through the two openings 24, 25 of the main tube21. The aerosol is provided to the inlet 32 of the fitting 30 and ledthrough the fitting 30 and the first opening 24 into the channel 26.Within the channel 26 the aerosol moves from the first opening 24 to thesecond opening 25. The aerosol is heated by the heater 23 andsemi-volatile material and semi-volatile particles of the aerosol areevaporated within the main tube 21. The evaporated semi-volatilematerial and semi-volatile particles can be adsorbed by the adsorbentmaterial 27. The remaining nonvolatile particles of the aerosol leavethe main tube 21 through the second opening 25 which is shown by anarrow. In this way, semi-volatile material and semi-volatile particlesare efficiently removed from the aerosol.

After the thermodenuder 20 has been operated for a certain time it isnecessary to remove the adsorbed semi-volatile material andsemi-volatile particles from the adsorbent material 27. This can be donein one of the following ways.

At first, it is possible to heat the main tube 21 from outside of themain tube 21. For this purpose an external further heater can bearranged adjacent to the outer wall 22. The further heater heats theadsorbent material 27 and the adsorbed semi-volatile material andsemi-volatile particles are evaporated. The evaporated semi-volatilematerial and semi-volatile particles can leave the main tube 21 throughthe second opening 25. In this way, the adsorbent material 27 isregenerated or cleaned.

At second, it is possible that the second side face 35 of the main tube21 is formed by a cap 31 that is reversibly attached to the main tube21. This means, the cap 31 can be removed so that the main tube 21 isopen at one of its side faces 35. Once the cap 31 is removed theadsorbent material 27 can be taken out of the main tube 21 replaced by anew adsorbent material 27.

A third possibility to remove semi-volatile material and semi-volatileparticles from the adsorbent material 27 is described with FIG. 2 .

FIG. 2 shows a cross section through another exemplary embodiment of thethermodenuder 20. The thermodenuder 20 has the same setup as shown inFIG. 1 with the only differences that a further channel 29 is arrangedbetween the outer wall 22 and the adsorbent material 27 and that afurther opening 36 is arranged within the first side face 34. Thismeans, in this case the adsorbent material 27 does not extend towardsthe outer wall 22. The further channel 29 fills the whole space betweenthe adsorbent material 27 and the outer wall 22. The further channel 29extends parallel to the channel 26. The further opening 36 is arrangedadjacent to the further channel 29.

For cleaning or regenerating the adsorbent material 27 a gas flow isprovided through the further opening 36 and the further channel 29. Thegas flows through the further channel 29 and the adsorbent material 27which is shown by arrows. The temperature of the gas is higher than thetemperature of the adsorbent material 27. Thus, the adsorbent material27 is heated by the gas. In this way, semi-volatile material andsemi-volatile particles adsorbed on or within the adsorbent material 27are evaporated. The gas is further led from the adsorbent material 27through the channel 26 out of the main tube 21. With this flow of gasthe evaporated semi-volatile material and semi-volatile particles aretransported from the adsorbent material 27 out of the main tube 21. Inthis way, the adsorbent material 27 is cleaned or regenerated.

FIG. 3 shows a cross section through another exemplary embodiment of thethermodenuder 20. The thermodenuder 20 has the same setup as shown inFIG. 1 with the only difference that the thermodenuder 20 does notcomprise the adsorbent material 27 and the inner tube 28. In this setupevaporated semi-volatile material and semi-volatile particles from theaerosol can adsorb at the outer wall 22 which has a lower temperaturethan the surroundings of the heater 23. In this way, semi-volatilematerial and semi-volatile particles can be removed from an aerosol.

REFERENCE NUMERALS

-   20: thermodenuder-   21: main tube-   22: outer wall-   23: heater-   24: first opening-   25: second opening-   26: channel-   27: adsorbent material-   28: inner tube-   29: further channel-   30: fitting-   31: cap-   32: inlet-   33: passage-   34: first side face-   35: second side face-   36: further opening-   x: main axis of extension

The invention claimed is:
 1. Thermodenuder comprising: a main tube with an outer wall, and a heater arranged within the main tube, wherein the heater is arranged in the center of a cross section through the main tube, the heater is spaced apart from the outer wall of the main tube, the main tube has a main axis of extension, the heater extends parallel to the main axis of extension of the main tube, the main tube has two openings which are arranged at opposing side faces of the main tube, and a channel for an aerosol is arranged within the main tube between the heater and the outer wall and between the two openings.
 2. Thermodenuder according to claim 1, wherein an adsorbent material is arranged within the main tube between the outer wall and the heater.
 3. Thermodenuder according to claim 2, wherein the adsorbent material is arranged spaced apart from heater.
 4. Thermodenuder according to claim 2, wherein the adsorbent material comprises ceramic fiber.
 5. Thermodenuder according to claim 2, wherein an inner tube is arranged within the main tube between the adsorbent material and the heater, where the inner tube is permeable for gases and the channel is arranged within the inner tube.
 6. Thermodenuder according to claim 2, wherein a further channel is arranged between the outer wall and the adsorbent material.
 7. Thermodenuder according to claim 1, wherein one of the openings is connected with a fitting.
 8. Thermodenuder according to claim 1, wherein the main tube has the shape of a cylinder.
 9. Thermodenuder according to claim 1, wherein the heater extends along at least 80% of the length of the main tube parallel to the main axis of extension of the main tube.
 10. Thermodenuder according to claim 1, wherein the channel is in direct contact with the heater.
 11. Thermodenuder according to claim 1, wherein one of the side faces of the main tube in which one of the openings is arranged is formed by a cap that is reversibly attached to the main tube.
 12. Method for removing semi-volatile material and semi-volatile particles from an aerosol, the method comprising the steps of: providing a main tube with an outer wall, where a heater is arranged within the main tube, heating a volume surrounding the heater by the heater, and leading an aerosol through the main tube and through two openings of the main tube where the two openings are arranged at opposing side faces of the main tube, wherein the heater is arranged in the center of a cross section through the main tube, the heater is spaced apart from the outer wall of the main tube, the main tube has a main axis of extension, the heater extends parallel to the main axis of extension of the main tube, and a channel for the aerosol is arranged within the main tube between the heater and the outer wall and between the two openings.
 13. Method according to claim 12, wherein semi-volatile material of the aerosol is evaporated within the main tube.
 14. Method according to claim 12, wherein the main tube is heated from outside of the main tube.
 15. Method according to claim 12, wherein a gas flow is provided through a further channel that is arranged between the outer wall and an adsorbent material that is arranged between the further channel and the channel. 